And I'm Robert Siegel. President Obama is shuffling his national security team. As he announced this afternoon, his longtime advisor Tom Donilon will be stepping down next month and Donilon will be replaced as national security advisor by Susan Rice. She is the U.S. ambassador to the United Nations, whose comments on last year's attack in Benghazi, Libya have made her a favorite target for Republicans.

To take Rice's place at the UN, the president named a prominent human rights activist and former aide, Samantha Power. NPR's Scott Horsley has more on these personnel changes.

SCOTT HORSLEY, BYLINE: Tom Donilon has been one of the president's top foreign policy advisors throughout his time in the White House and he's run the National Security Council for almost three years. During a rose garden send-off this afternoon, Obama said Donilon has made a big difference, delivering the president's daily security briefing almost every day.

PRESIDENT BARACK OBAMA: He's deftly advanced our strategic foreign policy initiatives while, at the same time, having to respond to unexpected crises and that happens just about every day.

HORSLEY: Donilon is one of the main architects behind the administration's stepped up focus on Asia, a fast growing part of the world that Obama believes was neglected under earlier presidents. Just last week, Donilon was in Beijing, helping to lay the groundwork for this weekend's summit meeting between Obama and Chinese President Xi Jinping.

OBAMA: He's worked tirelessly to forge a constructive relationship with China that advances our interests and our values. And I'm grateful that Tom will joining me as I meet with President Xi of China this week.

HORSLEY: Throughout his tenure, Donilon's kept a relatively low profile, generally working behind the scenes. His replacement, Susan Rice, is likely to be more visible, for better or worse. Rice became a lightning rod last year when she appeared on the Sunday talk shows days after the deadly attack in Benghazi, Libya and delivered talking points drafted by the intelligence community that turned out to be incorrect.

While emails released by the White House show Rice, herself, played little role in crafting those talking points, Senate Republicans attacked her performance and their opposition scuttled her chance of becoming Secretary of State. Unlike that post, her new job does not require Senate confirmation. The ranking Republican on the Senate Foreign Relations Committee, Bob Corker, said today he looks forward to working with Rice.

She, in turn, said she looks forward to working with leaders of both parties, as well as the government's national security apparatus in which she'll now play a central role.

AMBASSADOR SUSAN RICE: I admire the exemplary work done every day by our colleagues at State, Defense, the intelligence community and across the government to make our nation more secure.

HORSLEY: Obama's pick to replace Rice as U.N. ambassador is Samantha Power, a former journalist and White House advisor who's written passionately about the challenge of preventing genocide around the world. Power said whether the U.N. is up to that and other challenges is still an open question.

SAMANTHA POWER: I have seen U.N. aide workers enduring shell fire to deliver food to the people of Sudan, yet I've also seen U.N. peacekeepers fail to protect the people of Bosnia.

HORSLEY: News of these personnel changes comes as the president is preparing for a busy month of diplomacy with a G8 summit in Northern Ireland, a speech at the Brandenburg Gate in Germany, and a three-country tour of Africa on top of the summit with the Chinese president. At times like these, Obama may find himself doubly grateful for his staff.

OBAMA: I could not be prouder of these three individuals, not only their intelligence, not only their savvy, but their integrity and their heart.